body{
    overflow: hidden;
}
.loginbody{
    background-image:url("1.jpg");
    background-size: cover;
    overflow: hidden;
    margin: 0;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.fixed{
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.form-demo{
    position: relative;

    width: 400px;
    height: 600px;
}

/* 切换按钮所在的白色区域 */
.switch{
    background-color: #FCFBFA;
    width: 100%;
    height: 140px;
    position: absolute;
    left: 0;
    bottom: 0;
    border-radius: 8px;
    text-align: center;
}

/* 切换按钮 */
#change:checked+label,
    /* +用来选择同级后面最近的元素  */
#change:not(:checked)+label{
    background-color: #FFB8CE;
    color: white;
    width: 280px;
    padding: 8px 0;
    /* 用padding方便文字垂直居中 */
    font-size: 24px;
    font-weight: 600;
    position: absolute;
    bottom: 22px;
    left: 50%;
    transform: translate(-50%);
    border-radius: 8px;
    cursor: pointer;
    text-align: center;
}

/* 旋转体 */
.turn{
    width: 100%;
    height: 400px;
    position: absolute;
    top: 0;
    perspective: 800px;
    /* 旋转的时候的透视效果 */
}
.over{
    width: 100%;
    height: 100%;
    transform-style: preserve-3d;
    transition: all 1.6s ease;
    /* 旋转持续时间 */
    /* ease是慢快慢 */
}
#change:checked
~
.turn .over{
    transform: rotateY(180deg);
}
form{
    position: absolute;
    background-color: #FCFBFA;
    height: 100%;
    border-radius: 8px;
    transform-style: preserve-3d;
    text-align: center;
}
.sign{
    transform: rotateY(180deg);
}

h1, h2{
    color: #1f2029;
    user-select: none;
}
h1{
    margin-top: 38px;
    transform-style: preserve-3d;
    transform: translate3d(0, 0, 1px);
}

input{
    background-color: #4E495D;
    width: 70%;
    height: 48px;
    border-radius: 8px;
    margin-bottom: 20px;
    padding: 0 16px;
    font-size: 18px;
    color: #c4c3ca;
    font-weight: 500;
    outline: none;
    border: none;
    box-shadow: 0 4px 8px 0 rgba(78, 73, 79, .5);
    transform-style: preserve-3d;
    transform: translate3d(0, 0, 1px);
}
.login input:nth-child(-n+3){
    /* 选择class为login的子元素中的前三个input */
    margin: 20px 0;
}

.btn{
    background-color: rgba(19,51,101,0.41);
    border: none;
    width: 280px;
    font-size: 24px;
    font-weight: 600;
    padding: 6px 0;
    color: white;
    border-radius: 8px;
    margin-top: 15px;
    cursor: pointer;
}

